GSHHG is a "high-resolution geography data set, amalgamated from two databases: World Vector Shorelines (WVS) and CIA World Data Bank II (WDBII)", see https://www.ngdc.noaa.gov/mgg/shorelines/
The files are provided as ESRI shapefiles and in a native binary format.
The native binary format is pretty simple and documented here:
https://www.ngdc.noaa.gov/mgg/shorelines/data/gshhg/latest/readme.txt
This is a loader for this binary format.
Berke DURAK bd@exhrd.fr